Data was collected for 315 randomly selected 10 minute intervals. For each ten-minute interval, the number of people entering the atrium of a large mall were recorded. The data is summarized in the table below.

Number   of Guests	Frequency
100 – 109	86
110 – 119	11
120 – 129	54
130 – 139	98
140 – 149	66

What is the class width for this GFDT?

Class width =